Elevator door monitor and drive safety apparatus

ABSTRACT

A safety apparatus for elevator apparatuses which can move a cab by way of a drive, including: a first safety circuit, which has a closed conduction state and an open conduction state, with an interrupting apparatus for interrupting the drive depending on the conduction state of the first safety circuit, a safety device, which includes at least two sensors, which can be switched between at least two switching states depending on the closing state of the elevator door. In order to be able to improve the susceptibility to maintenance, a switching unit is provided which can be switched between at least two switching states by connection to the safety device and is designed to effect the closed and/or open conduction state of the first safety circuit.

FIELD OF THE INVENTION

The invention relates to a safety apparatus for elevator apparatuses, aswell as a method for retrofitting an elevator apparatus and aretrofitting apparatus therefor.

BACKGROUND OF THE INVENTION

The prior art has disclosed conventional safety apparatuses forelevators which use electrical or electromechanical contacts andswitches in order to determine the locking or closing state of anelevator door. The intention here is for an elevator cab to only beallowed to travel when all the doors are locked.

The object of the invention is to propose a safety apparatus and anelevator apparatus in which the susceptibility to the need formaintenance can be improved.

The object is achieved, starting from a safety apparatus and an elevatorapparatus of the type mentioned at the outset.

SUMMARY OF THE INVENTION

By virtue of the measures mentioned hereinafter, advantageousdevelopments and embodiments of the invention are possible.

Correspondingly, a safety apparatus for elevator apparatuses which canmove a cab by means of a drive comprising: a first safety circuit, whichhas a closed conduction state and an open conduction state, with aninterrupting apparatus for interrupting the drive depending on theconduction state of the first safety circuit, and an additional safetydevice, which comprises at least two sensors, which can be switchedbetween at least two switching states depending on the closing state ofthe elevator door, is characterized by the fact that a switching unit isprovided which can be switched between at least two switching states byconnection to the safety device. In addition, the switching unit isdesigned to effect the closed and/or open conduction state of the firstsafety circuit. The interrupting apparatus serves the purpose ofinterrupting the drive, with the interruption being dependent on thenature of the switching states of the switching unit and furthermoreother switches in the first safety circuit, i.e. on whether all of thedoors are actually locked. This measure makes it possible tocorrespondingly improve the susceptibility to the need for maintenanceand to increase the safety of the elevator.

If a plurality of doors is provided, travel can only be begun orcontinued when all of the doors are locked. Correspondingly, it isexpedient if the corresponding sensors which are each assigned to a doorare connected in series.

The first safety circuit has, for example, normally closed switches anda relay/contactor as the interrupting apparatus. The normally closedswitches can be in the form of electromechanical switches inconventional safety circuits. If an open conduction state is effected,i.e. the first safety circuit is interrupted, the relay or the contactoralso opens and interrupts a motor of the elevator, for example.

The safety device can to a certain extent be considered to be anequivalent circuit for individual normally closed switches or for all ofthe normally closed switches which monitor the closing state or lockingstate of the door. In principle, the safety device may also be a secondsafety circuit.

Correspondingly, in one embodiment of the invention, the safety devicecan be in the form of a second safety circuit which comprises at leasttwo sensors which can be switched between at least two switching statesdepending on the closing state of the elevator door. However, theinterrupting apparatus can be designed to interrupt and/or continue thedrive, inter alia depending on the switching state of a switching unit(not of the sensor directly). The switching unit can in turn be switchedbetween at least two switching states by connection to the safetycircuit. The interrupting apparatus and the switching of theinterrupting apparatus are therefore dependent on the safety circuit,but are not coupled directly to said safety circuit, but indirectly viaan interposed switching unit. This apparatus makes it possible to acertain extent for the safety circuit or the arrangement of sensors tobe “decoupled” as a separate apparatus. This can be advantageous inparticular when an apparatus with comparatively high voltages isrequired for the interrupting apparatus. Such an apparatus is associatedwith corresponding disadvantages in terms of fitting and maintenancesince there is the possibility that contact could be made with liveparts carrying a relatively high voltage; these disadvantages can becircumvented with the safety apparatus according to the invention. Thesafety circuit itself can in principle be, operated on relatively lowvoltages, however.

In addition, the sensors can in turn be connected in series. Inparticular, when such decoupling has taken place, it is possiblyadvantageous to identify a fault state of a sensor. In a conventionalseries circuit, however, it is in principle not possible to perceivewhich sensor might have been interrupted by a defect. In the case of alarge number of sensors, this requires a corresponding amount of timeand therefore also corresponding costs during maintenance. This can becounteracted by virtue of the fact that an indicator apparatus forindicating the switching state of the individual sensors with assignmentof the individual switching states to the corresponding sensors isprovided. In principle, a corresponding indicator apparatus is capableof indicating which of the sensors has which switching state at thattime or which sensor does not have a specific switching state at thattime, for example which sensor is open.

In particular, in a development of the invention, the safety device canalso be in the form of a bus system, the sensors each having anelectronics unit. In addition, the sensor is connected to the bus viaits corresponding electronics unit. Such a bus makes it possible inparticular to transmit and/or interchange data. For example, data ofindividual sensors can thus be read on command. In principle, abidirectionally operating bus is conceivable in which data can betransmitted and received. In principle, however, a unidirectional bus isalso conceivable. As data it is possible to transmit the switchingstates, but it is also possible for identification data of the sensorsto be transmitted which give information on which sensor is the sensorin question. These identification data can also be addressings of theindividual sensors, for example. This makes it possible, in aparticularly elegant manner, to read which sensor is indicating aspecific state at that time. In addition, bus systems can also operateparticularly quickly, if appropriate.

In a preferred development of the invention, at least one of the sensorshas the following construction: a sensor for safety apparatuses forelevator apparatuses which can move a cab by means of a drive, thesensor being in the form of an optical sensor which comprises atransmitter for transmitting an optical signal and a receiver forreceiving the optical signal. A particularly advantageous feature of thesensor is that it can operate in contactless fashion, i.e. without anywear as well. In addition, the sensor therefore does not have any livecontact areas, or only has a few live contact areas, and is furthermoresafe during fitting. The sensor according to the invention can thereforereplace a conventional switch, a so-called interlock switch, from theprior art. In addition, the sensor provides the possibility of therebeing no need for the circuit to be interrupted, in contrast to anelectromechanical switch.

By virtue of the sensor, it is also possible to avoid a defect which canoccur, for example in the case of electromechanical sensors andcontacts, as a result of contact erosion owing to flashover duringopening or closing of the electrical contacts and can ultimately resultin a loss of function.

Owing to the fact that the circuit does not need to be interrupted withthis sensor, in contrast to a switch, improved diagnosis in the case ofdefects is advantageously possible.

In addition, a contact bridge and a contact receptacle for receiving thecontact bridge are provided which are arranged in such a way that theclosing state of the elevator door can be determined by connection ofthe contact receptacle and the contact bridge. The detection state ofthe sensor is therefore dependent on the proximity of the contact bridgeto the contact receptacle.

An elevator itself generally has firstly a cab which can be movedbetween individual stories or floors. The individual floors each haveshaft openings, in the region of which the cab can be moved into a stopposition when said cab is intended to travel to the corresponding floor.In this stop position, access to the cab is then enabled. This accesscan be enabled by virtue of the elevator doors being opened and thenclosed again and locked prior to continued travel of the elevator.Elevator doors may be shaft doors or cab doors. The shaft doors arefitted or mounted movably on the shaft itself in the region of the shaftopening. The cab doors are in turn fitted or mounted movably on the cab.In general, in each case one cab door is assigned to a shaft door, withthe two being arranged so as to overlap one another (so as to overlapone another at least partially) in the stop position. Generally, saiddoors are also moved at least substantially synchronously.

In order that a journey in the cab can be begun or that the cab cancontinue to travel, it is necessary for all of the doors to be closedand locked. This can be checked by means of corresponding safetyapparatuses which can possibly stop the drive by means of an interrupterapparatus. In principle, the interrupting apparatus or interruptioncircuit can activate the monitoring unit, i.e. controller or regulator,of the motor or the drive, with the result that said monitoring unitstops the drive; it is also conceivable for the interrupting apparatusto directly interrupt the power supply to the drive/motor.

The corresponding sensor is therefore designed to check whether thecorresponding door of an elevator or a shaft is open or closed andlocked. In the present case, it is particularly advantageous for thesensor to have a similar design to a plug-type connection, with theresult that a contact bridge can engage in a contact shaft. In addition,this measure provides the possibility of an apparatus which ismechanically very stable. In principle, the sensor can be designed insuch a way that the contact bridge is accommodated in the shaft of thecontact receptacle with play or in interlocking fashion.

In addition, the contact bridge is designed in such a way that itcomprises at least one transmission element for transmitting an opticalsignal. This advantageously makes it possible in particular to achieve aso-called failsafe circuit. Only when the contact bridge has reached aparticular position by corresponding connection to the contactreceptacle when the door is closed, is it possible for correspondingenabling for travel to be issued. In the case of simply a light barrier,this would in principle not be the case: the transmission element can bedesigned in such a way that the transmission of the optical signal takesplace in a particular way which can only be manipulated withconsiderable difficulty and can also not readily be realized byaccident. In the case of a simple light barrier, for example, whichwould be interrupted when the door is closed, this would mean that thedrive would also be enabled when, for example, a corresponding object, afly or the like interrupts the light barrier.

A further option is to arrange the transmitter or the receiver on thecontact receptacle. The transmission of light by means of thetransmission element can then only take place via the contact bridge.This design enables a particularly compact construction.

One possibility consists in designing the transmission element as areflective surface, with this reflective surface then reflecting theoptical signal or the light and only in this way guiding it onto thecorresponding receiver. The reflective surface can be arranged in anotch in the contact bridge, for example. However, it is alsoconceivable for the transmission element to be an optical medium. It isconceivable, for example, for the light refraction to be utilized in thetransition from the air into this optical medium and the light beam istherefore directed in a certain direction, with the result that onlythen is it guided either onto the receiver or not onto the receiver.

In addition, a fiberoptic conductor can be provided as optical medium.The optical signal is transmitted when the light from said signal iscoupled into the fiberoptic conductor, propagates through the fiberopticconductor and passes into the receiver via the fiberoptic conductor.

It is particularly advantageous to design the transmitter as alight-emitting diode and/or the receiver as a photodiode. Particularlycheap standard electronic components can be used; this results in thepossibility of particular cost savings.

Moreover, it is also conceivable for the contact receptacle to comprisetransmission elements for transmitting the optical signal, for examplereflective surfaces or optical media such as fiberoptic conductors, forexample. It is conceivable for a subsection of the propagation path ofthe optical signal from the transmitter to the receiver to be over areflective surface or through a fiberoptic conductor in the contactreceptacle. It is also conceivable for the fiberoptic conductor in thecontact receptacle or in the contact bridge to be shifted, by virtue ofthe contact bridge being received, in such a way that transmission ofthe light is enabled.

Furthermore, the sensor can comprise an electronics unit for theevaluation of the receiver, said electronics unit being designed tointerpret the evaluation of the receiver in one of the switching statesand/or into an electrical signal. This means that the electronics unitis designed to generate an electrical signal or produce an electricalcontact. However, since the mechanical closing state is detected purelyoptically, this means that it is not absolutely necessary for amechanical contact or a mechanical opening state to be produced in orderto produce an electrical signal. It is conceivable, for example, for theoptical signal to enable the receiver, for example a photodiode, andtherefore for it to be possible for a conduction state to be reached (incontrast to an interruption). As a result, an interpretation of theswitching state of the sensor is performed electronically to a certainextent. However, the electronics unit can also additionally be designedto enable a connection to further electronics. For example, it can alsobe designed to enable a connection to a bus. This design makes itpossible in particular to improve the relatively low susceptibility tothe need for maintenance even further since mechanical contacts andsensors are substantially avoided. It is also particularly advantageousthat it is merely necessary for the contact bridge to enter the contactreceptacle as the mechanical contact closure.

In order that no parasitic light passes accidentally from thetransmitter into the receiver, an isolating web for optically isolatingthe transmitter and the receiver can also be provided. This once againreduces in principle the possibility of errors occurring as a result ofan incorrect interpretation of the signals. In addition, a diffuser canmoreover also be provided, said diffuser distributing parasitic lightdiffusely. It is also conceivable for the receiver to be set during thedetection to a certain threshold value as regards the intensity of theincident light, with the result that, in the case of a certain amount ofparasitic light which possibly enters the receiver, a correspondingsequential signal which should only be resolved when light enters thereceiver via the transmission element is nevertheless not triggered.

A connection can be produced so as to be particularly robust, forexample, in which the contact receptacle comprises a shaft and thecontact bridge comprises a tongue-shaped lug, which engages in the shaftduring connection of contact bridge and contact receptacle. It isparticularly advantageous here also that corresponding coding can beperformed, i.e. the contact bridge, in a similar way to a key, needs tobe provided with a particular design in order for it to be able to enterthe contact receptacle. In particular, this can increase the safety ofthis apparatus, in particular when the contact receptacle shaft isdesigned in such a way that it is not possible for a hand to gainaccess.

It is likewise possible in the case of a corresponding sensor to provideat least two transmission elements which are arranged in series in themovement direction of the contact bridge, which means that, when thedoor is locked, the contact bridge dips correspondingly into the contactreceptacle and is initially visible for the optical signal and theoptical light beam of one of the transmission elements (namely the firsttransmission element in the movement direction). As the movementprogresses, the next transmission element then becomes visible, whilethe previous transmission element is pushed out of the optical path. Itis thus possible for a plurality of optical signals to occur with atemporal offset. In addition, it is conceivable to design theelectronics unit or to pass on the corresponding signals to a furtherevaluation unit so that the occurrence of the corresponding signals isdetermined as a function of time, for example. It is thus possible forconclusions to be drawn in respect of the speed of the locking process.This also makes it possible to draw a conclusion in respect, of thefunctional and maintenance state of the locking device of the doors. Inprinciple, the locking process and not the door lock is moreovermonitored. Depending on the way in which the corresponding transmissionelements are arranged and how many of the transmission elements arearranged, the precision of such a determination can possibly beincreased.

In principle, the first safety circuit can also furthermore haveelectromechanical normally closed switches. Said switches are possiblyintended to be retained in an existing elevator system, for example, andnot to be correspondingly replaced by optical sensors duringretrofitting, for example. Optical sensors can be provided in particularfor checking the correct locking of elevator doors. If the elevator isintended to be stopped during its movement even when the locking has notbeen correctly performed, however, but there is another fault,electromechanical normally closed switches can also continue to be usedfor checking such faults, if appropriate.

The sensors and/or normally closed switches can be connected in seriesin order for the drive to be stopped in the event of an interruption.Therefore, the circuit corresponds to an AND circuit, i.e. the motoronly runs when all of the sensors or normally closed switches completethe circuit and do not interrupt the line.

Likewise, a corresponding indicator apparatus can be provided whichmakes it possible, for example, to identify which of the sensors has aspecific switching state at that time and is possibly defective.

Furthermore, the sensor can comprise an electronics unit for theevaluation of the receiver, said electronics unit being designed tointerpret the evaluation of the receiver in one of the switching statesand/or into an electrical signal. This means that the electronics unitis designed to generate an electrical signal or produce an electricalcontact. However, since the mechanical closing state is detected purelyoptically, this means that it is not absolutely necessary for amechanical contact or a mechanical opening state to be produced in orderto produce an electrical signal. It is conceivable, for example, for theoptical signal to enable the receiver, for example a photodiode, andtherefore for it to be possible for a conduction state to be reached (incontrast to an interruption). As a result, an interpretation of theswitching state of the sensor is performed electronically to a certainextent. However, the electronics unit can also additionally be designedto enable a connection to further electronics. For example, it can alsobe designed to enable a connection to a bus. This design makes itpossible in particular to improve the relatively low susceptibility tothe need for maintenance even further since mechanical contacts andsensors are substantially avoided. It is also particularly advantageousthat it is merely necessary for the contact bridge to enter the contactreceptacle as the mechanical contact closure.

In one development of the invention, the electronics unit is forcommunication with a switching unit, in particular for transmission ofswitching states and/or identification signals. The switching unit is acomponent part which can be used to open or close a line by virtue of aswitching operation, in a similar way to in the case of a relay orcontactor. However, the switching operation is triggered when acorresponding signal or a corresponding item of information is passed onto the switching unit from the sensors. In particular, it isadvantageous that the line between the switching unit and the sensor nolonger needs to be interrupted, as is often the case in the case of acontactor/relay, for example.

The electronics unit can in particular be arranged in or on the contactreceptacle in which the transmitter and receiver are also arranged. Thecontact receptacle can be arranged, for example statically, in theelevator apparatus, while the contact bridge is arranged on a movingpart and merely represents the “key” in order to enable signaltransmission in the contact receptacle.

A sensor can comprise precisely two terminals which are used firstly forpower supply and secondly for communication with the electronics unit.The same line which is also used for power supply is therefore used forthe communication. This measure enables a particularly compact andinexpensive design. In addition, this means that no additional lines orterminals need to be laid during retrofitting, when a conventionalsensor is replaced by a sensor according to the invention, for example.

In addition, in the case of a sensor the communication can take placevia modulation of its internal resistance of the sensor. In the circuitwith the switching unit, the voltage and/or the current intensity canthus be modulated depending on the circuitry. This modulation thencarries the information which is intended to be transmitted during thecommunication. For example, a circuit which comprises sensors connectedin series and a switching unit (likewise connected in series) isconceivable. If the resistance of a sensor in the case of sensorsconnected in series is changed, the current intensity changes. If, forexample, a constant current source is used for the circuit, a change inthe resistance has the effect that the voltage needs to be increased inorder to compensate for the resulting reduction in the current intensitywhich is initially caused by the lower resistance. The modulation cantherefore act as an information carrier. The changes in the currentintensity or voltage can be measured and can be interpreted asinformation.

In turn, in one development of the invention, the switching unit isdesigned to perform the communication with the sensors by modulation ofthe current intensity or the voltage. This measure can be performed byvirtue of changes in resistances or corresponding changes in or matchingof voltage or current intensity.

In the case of a series circuit, it is particularly advantageous if thesensor has a low transfer resistance. The resistance of a sensor can be,for example, in the range of from 1 ohm to 100 ohms, in particular inthe range of from ohms to 20 ohms, preferably less than 10 ohms.Precisely in the case of a series circuit, it is advantageous to designthe transfer resistance to be as low as possible, in particular lowerthan 10 ohms, in order that the voltage drop across the sensor is notexcessively high.

Correspondingly, in addition an elevator apparatus according to theinvention with a cab and at least one elevator door for opening and/orclosing the cab and with a safety apparatus is characterized by the factthat a safety apparatus according to the invention are provided. As aresult, the above-explained advantages can be used directly, inter alia.

It is conceivable in particular for the contact bridge to be fitted toan elevator door and for the contact receptacle to be fitted to the cabitself. In principle, however, a reverse design is also conceivable,namely the contact receptacle on the elevator door and the contactbridge on the cab. Similarly, the contact bridge and the contactreceptacle can also be arranged on the shaft door and on the shaft orthe shaft frame.

The contact receptacle itself can furthermore have a housing withfitting elements and the above-described insertion slot for the contactbridge. The electronics unit can be equipped with a light-emitting diode(LED) as fiberoptic conductor printed circuit board (PCB) and isequipped with a corresponding photodiode as receiver. The isolating webcan correspondingly be arranged between the transmitter and thereceiver. In addition, it is also conceivable for correspondingcontacts, for example for making contact with the photodiode, to enablea connection to a corresponding electronics unit. The electronics unitcan also be provided as a separate component part or so as to beintegrated in another part of the elevator. In principle, the opticalcontact between the transmitter and the receiver can be converted intoan electrical signal to a certain extent. In turn, the contact bridgecan have a mounting plate, namely a corresponding tongue with opticalfibers, wherein in this case the corresponding optical fibers canconduct light from the LED to the photodiode when the tongue isinserted. If appropriate, the corresponding parts can in particular alsobe prefitted.

A particular advantage of the subject matter according to the inventionis that virtually no live contact areas are provided, i.e. fitting isvery safe. The evaluation of the speed of the increase in illuminationat the photodiode or the sequence of light pulses of two lighttransmission elements makes it possible to draw a conclusion in respectof the speed of the locking of the door with reference to themaintenance state. In addition, items of information relating to themaintenance state or the aging of the apparatus can thus be determined.In addition, an evaluation of the final illumination intensity can beperformed in connection with the development of the illumination overtime. This can make it possible in particular to draw a conclusion withregard to the insertion depth and also the locking safety. A pluralityof transmission elements also enable dynamic detection. In addition, itis conceivable to increase the robustness by virtue of providing designmeasures which envisage the LED or the photodiode being covered.Precisely the design of a contact receptacle in the form of a shaftmakes this particularly advantageously possible.

As has already been mentioned, a separate evaluation unit can beprovided which can communicate with the corresponding bus via aninterface, for example. A particular advantage of the apparatusaccording to the invention is that no interruption of an electricalcontact is envisaged, but merely transmission of a signal optically isenabled or prevented.

A further advantage of the invention consists in that the apparatusaccording to the invention can be retrofitted particularly easily. In anexisting elevator system, until now it has been particularlydisadvantageous that virtually all of the sensors in the individualstories need to be investigated separately in the event of a defect inone sensor. In addition, it may not be possible to identify whether thedefect is in a single sensor or a plurality of sensors, with the resultthat all of the sensors may need to be checked. The states of thesensors, i.e. defective or not or open or not, can be indicatedcentrally via an evaluation unit also in a convenient manner using acomputer, control panel or the like.

In a corresponding retrofitting method according to the invention, thesafety device can be used as a replacement part. The connection to thenormally closed switches, for example conventional electromechanicalswitches, can be capped. Instead, the switching unit of the safetydevice is connected. In the case of elevators, the retrofittingcomplexity can therefore be considerably reduced. It is generallysufficient to draw in a relatively long connecting line over thestories. Both lines to the old normally closed switches can in additionusually be capped in uncomplicated fashion at a location in the vicinityof the control center.

In connection with the retrofitting, a retrofitting apparatus isinstalled in a corresponding elevator apparatus which is to beretrofitted, the elevator apparatus having a safety circuit which, inthe context of the invention, corresponds to the first safety circuitand has normally closed switches. The retrofitting apparatus accordingto the invention comprises sensors which can be switched between atleast two switching states depending on the closing state of theelevator door. Furthermore, the retrofitting apparatus comprises aswitching unit which can be used instead of the normally closed switcheswhich are intended to be replaced. The switching unit can be switched bymeans of the sensors. The sensors and the switching unit can interchangeinformation, for example via modulation of the voltage/current intensityor the internal resistance of the sensors.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are illustrated in the drawingsand will be explained in more detail below with further details andadvantages being given.

Specifically, in the drawings:

FIG. 1 shows a sensor comprising a contact bridge with reflective stripsand a contact receptacle in accordance with the invention,

FIG. 2 shows a contact receptacle in accordance with the invention,

FIG. 3 shows a contact bridge with reflective strips in accordance withthe invention,

FIG. 4 shows a sensor comprising a contact bridge with a fiberopticconductor and a contact receptacle in accordance with the invention,

FIG. 5 shows a contact receptacle in accordance with the invention, asin FIG. 2,

FIG. 6 shows a contact bridge with a fiberoptic conductor in accordancewith the invention,

FIG. 7 shows the connection (temporal sequence) of the contact bridgeand contact receptacle in accordance with the invention,

FIG. 8 shows a sensor with reflective strips in accordance with theinvention,

FIG. 9 shows a safety apparatus with sensors in accordance with theinvention,

FIG. 10 shows a safety apparatus with a safety circuit in accordancewith the invention,

FIG. 11 shows a safety apparatus with a bus in accordance with theinvention,

FIG. 12 shows a safety apparatus with a bus and an integrated contactorin the switching unit in accordance with the invention,

FIG. 13 shows a circuit diagram for an elevator in accordance with theinvention,

FIG. 14 shows a sensor with fiberoptic conductors in accordance with theinvention,

FIG. 15 shows a perspective view of the sensor shown in FIG. 14, and

FIG. 16 shows a schematic illustration illustrating the way in whichcommunication with individual sensors takes place in a safety apparatusin accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a sensor 1 with a contact receptacle 2 (shaft) and acontact bridge 3, the contact bridge having reflective strips 9, whichreflect light emitted from a transmitter of the contact receptacle 2 inthe direction of a receiver of the contact receptacle 2.

In turn, FIG. 2 shows the corresponding contact receptacle 2 with atransmitter 4 and a receiver 5, with an isolating web 6 being arrangedbetween said transmitter and said receiver, to be precise in a frontview, a side view and a plan view. Fitting apparatuses or fitting aidsare indicated by the reference symbol 7. The contact receptacle 2 hasadditional electrical terminals, via which the sensor 1 can be connectedto the rest of the sensor apparatus or to the safety circuit.

FIG. 3 shows a contact bridge in different views, to be precise in afront view, a side view and a plan view. Said contact bridge alsocomprises corresponding fitting aids 8. Slots are incorporated into thecontact bridge 3 as transmission elements 9, said slots each havingreflective surfaces. In total there are three reflection units 9 a, 9 b,9 c, with the result that dynamic contact detection is enabled to acertain extent since first the reflection unit 9 a, then the reflectionunit 9 b and finally 9 c enter the contact receptacle 2 or the opticalpath when the contact bridge 3 is inserted and therefore dynamicmeasurement of the signal with temporal dependence is possible.

FIG. 4 shows a sensor 1′ with a contact receptacle 2 (shaft) and acontact bridge 3′, the contact bridge having a fiberoptic conductor; thelight emitted by a transmitter of the contact receptacle 2 passes intothe fiberoptic conductor inlet 4′, propagates through the fiberopticconductor and emerges from the fiberoptic conductor outlet 5′ again,with the result that it passes to the receiver of the contact receptacle2.

In turn, FIG. 5 shows the corresponding contact receptacle 2, as hasalready been described in relation to FIG. 2, said contact receptaclealso being suitable for a sensor 1′ with a fiberoptic conductor.

FIG. 6 shows a contact bridge 3′ in different views, to be precise in afront view, a side view and a plan view. Said contact bridge alsocomprises corresponding fitting aids 8. A fiberoptic conductor isincorporated into the contact bridge 3′ as transmission element L andthe light signal transmitted by the contact receptacle can propagatethrough said fiberoptic conductor. The figure also shows the light inlet4′ and the light outlet 5′.

FIG. 7 shows the contact bridge 3 (with reflective strips) entering thecontact receptacle 2 in this way, with the contact bridge not yet beingconnected to the contact receptacle 2 in situation A. In situation B,the reflection unit 9 a has just entered in the region of the opticalpath and transmits the light path from the transmitter to the receiver.In situation C, the contact bridge 3 is positioned at this time suchthat the optical signal is interrupted since the contact bridge 3, interms of its height, is precisely between the reflection units 9 b and 9c and the optical path is therefore interrupted. Only in situation D isthe contact bridge, which has been completely inserted into the contactreceptacle 2, in such a position that the optical path is notinterrupted and light can pass from the receiver 4 into thedetector/photodiode via the reflection element 9 c. The reflection units9, and also other transmission units such as optical media, can havedifferent forms and provide characteristic reflections or lighttransmissions, with the result that these can each be identified, ifappropriate, by means of the receiver or the electronics unit as well.

FIG. 8 shows a similar illustration in which the contact bridge 3 entersthe contact receptacle 2.

In turn, FIG. 9 shows a safety apparatus with a plurality of opticalsensors 10, which are all connected in series. Furthermore, a series offurther electromechanical normally closed switches 11 is provided whichcan otherwise be used in connection with an elevator. In addition, avoltage source 13 is provided. All of these switches or sensors 11 and10 are connected in series and are connected to a switching unit 12.This circuit comprising a series circuit comprising the switches 11, thesensors 10 and the switching unit 12 forms a safety circuit. If one ofthe switches 11 is interrupted, the entire circuit is interrupted, andthe switching unit 12 disconnects the motor M, which represents thedrive for the elevator cab. The switches 11 can be normally closedswitches of the known type. If one of the sensors 10 detects that theelevator has not been locked properly, for example, said sensortransmits a corresponding signal via the circuit, and this signal isreceived by the communication unit of the switching unit 12, with theresult that said unit can disconnect the motor M. Correspondingly, theswitching unit 12 partially takes over the function of your relay; inaddition, switching operations of the switching unit are also dependenton signals from the sensors, however. The switching unit 12 thereforedoes not only respond to line interruptions.

FIG. 10 shows a safety apparatus with a safety device, namely a (second)safety circuit 14, with corresponding optical sensors 10. This safetycircuit is connected to the first safety circuit 16 via a switching unit12′, said first safety circuit in turn having further sensors 11. Theswitching unit 12′ is similar to the switching unit 12 and has the samemode of operation; in this case, in contrast to the switching unit 12shown in FIG. 9, however, the voltage source is also integrated in theswitching unit 12′. A contactor/relay 15, which can in turn disconnect adrive M, is located in the first safety circuit 16. The contactor 15 ismerely designed to disconnect the motor M in the event of a lineinterruption in the circuit 16. If one of the sensors 10 is interruptedoptically, the switching unit 12′ is also interrupted, and therefore theline in the first safety circuit 16. The contactor 15 disconnects themotor M. Instead of the conventional normally closed switches, thesensors according to the invention are combined in a dedicated safetycircuit 14 and are connected to the original, first safety circuit 16via the switching unit 12′. The safety circuit 16 can in this casepartly use the wiring of the original safety apparatus.

In addition, FIG. 10 illustrates how retrofitting of a conventionalapparatus can be performed by virtue of the original first safetycircuit 16 being capped at the points U and the second safety circuit 14with the switching unit 12′ being used correspondingly. It is then onlynecessary for a relatively long cable K to be drawn in.

FIG. 11 shows a corresponding apparatus in which, instead of a secondsafety circuit, a bus 20 is arranged as the safety device. Thecorresponding sensors 21 have an electronics unit which enable aconnection to the corresponding bus 20. The bus is likewise connected toa switching unit 25, with the result that when one of the opticalsensors 21 is interrupted, said sensor in turn transmits a signal to theswitching unit 25 which in turn interrupts the first safety circuit 26.Owing to the interrupted line of the safety circuit 26, the motor M isdisconnected by the contactor 15. The switching unit 25 can form themaster in the bus, for example, while the sensors 21 have a slaveconfiguration.

FIG. 12 shows a similar apparatus to that shown in FIG. 8, but in thiscase the contactor 15 is additionally integrated in the switching unit27, with the contactor disconnecting the motor, if appropriate.

FIG. 13 shows an exemplary circuit diagram 30 for an elevator inaccordance with the invention.

FIG. 14 shows a sensor 41 in a plan view and in a side view with acontact receptacle 42 and a contact bridge 43, in which a fiberopticconductor 44 is arranged. In this case, the contact bridge 43 is overallin the form of a fiberoptic conductor 44, i.e. consists of thecorresponding optical medium. The contact receptacle 42 comprises atransmitter 45 and a receiver 46 for transmitting/receiving opticalsignals. The optical signal transmitted by the transmitter 45 canpropagate through the fiberoptic conductor 44, as soon as the contactreceptacle 42 has received the contact bridge 43, and therefore passesinto the receiver 46. The contact bridge 43 (or the fiberoptic conductor44) is in the form of a U and, when it is plugged into the contactreceptacle 42, engages only with both limbs in the two shafts of thecontact receptacle 42. The fiberoptic conductor 44 correspondinglylikewise has a U-shaped design. FIG. 15 in turn shows the sensor 41 in aperspective view.

FIG. 16 shows a schematic illustration of the communication in thesafety circuit 14 between the controller 57 of the switching unit andthe individual sensors 10 or microcontrollers μC thereof. Thecommunication from the controller 57 to the individual sensors takesplace via current modulation, while, conversely, that from the sensor 10to the controller 57 takes place via voltage modulation.

It is generally necessary for notable current or voltage changes ormodulations to take place since, owing to the long cable lengthsoccurring in an elevator system, the change would otherwise beunnoticeable. For example, current changes in the region of a factor of3 are conceivable.

The units 50, 51 each correspond to a sensor. Variable resistors aredenoted by the reference symbols 52, 53. Each sensor is assigned avariable resistor. The resistance can be changed in different ways: itis conceivable for resistors to be added into this circuit in parallelwith other resistors, as a result of which the total resistance iscorrespondingly reduced. However, it is also conceivable for theresistance to be influenced by means of the circuitry used, for exampleby individual transistors being switched off. The change in resistancecan be influenced optically, for example by means of phototransistors,photodiodes, optocouplers or the like.

The circuit comprises constant current sources 54, 55, which are eachdesigned to match their voltage in the event of a change in theresistance in the circuit in such a way that a constant current flows. Achange in the resistance (communication: controller 57 to sensor 10)regulates the constant current source 54 to a constant currentintensity, with the result that the voltage measured via the voltmeter56 changes.

If a further constant current source 55 is added into the circuit, thecurrent intensity can also be modulated, i.e. the voltage does notremain constant (communication: sensor to controller). The change in thevoltage applied to the circuit can be determined by the voltmeter 58.

The states of the individual sensors or other data relating to thesensors can therefore be output via an output 60. The relay 59 iscontrolled corresponding to the sensors via the microcontroller 57.

FIG. 16 illustrates a switching unit 12″, as is also illustrated in FIG.9 as switching unit 12 or in FIG. 10 as switching unit 12′. Theswitching unit 12′ also comprises a voltage source. The switching unit12 from FIG. 9 in particular also comprises the function of a relay,which can disconnect the motor M in the event of a line interruption aswell. The switching unit 12 is connected to a (second) safety circuit 14in FIG. 16.

LIST OF REFERENCE SYMBOLS

-   1 Sensor-   1′ Sensor-   2 Contact receptacle-   3 Contact bridge-   3′ Contact bridge-   4 Transmitter-   4′ Fiberoptic conductor inlet-   5 Receiver-   5′ Fiberoptic conductor outlet-   6 Isolating web-   7 Fitting unit-   8 Fitting unit-   9 Reflective surface-   9 a Reflective surface-   9 b Reflective surface-   9 c Reflective surface-   10 Optical sensor-   11 Electromechanical normally closed switch-   12 Switching unit-   12′ Switching unit (with voltage source)-   12″ Switching unit-   13 Voltage source-   14 Second safety circuit-   15 Contactor/relay-   16 First safety circuit-   20 Bus-   21 Optical sensor with electronics unit-   25 Switching unit-   26 Safety circuit-   27 Switching unit with integrated contactor-   30 Circuit diagram-   41 Sensor-   42 Contact receptacle-   43 Contact bridge-   44 Fiberoptic conductor-   45 Transmitter-   46 Receiver-   50 Communication unit-   51 Communication unit-   52 Variable resistor-   53 Variable resistor-   54 Constant current source-   55 Constant current source-   56 Voltmeter-   57 Microcontroller of switching unit-   58 Voltmeter-   59 Relay-   60 Output-   A View at first time-   B View at second time-   C View at third time-   D View at fourth time-   K Cable/electrical line-   L Fiberoptic conductor-   M Drive motor-   μC Microcontroller of a sensor-   U Interruption

The invention claimed is:
 1. A safety apparatus for elevator apparatuseswhich can move a cab by means of a drive, comprising: a first safetycircuit that has a closed conduction state and an open conduction state,with an interrupting apparatus for interrupting the drive depending onthe conduction state of the first safety circuit, a safety devicecomprising at least two sensors, which can be switched between at leasttwo switching states depending on the closing state of an elevator door,and a switching unit that can be switched between at least two switchingstates by connection to the safety device to effect at least one of theclosed and open conduction state of the first safety circuit, whereinthe switching state of each sensor is indicated independent of theswitching states of the at least two sensors.
 2. A safety apparatusaccording to claim 1, wherein the safety device is in the form of asecond safety circuit.
 3. A safety apparatus according to claim 1,wherein the safety device is in the form of a bus system, the sensorseach having an electronics unit which is connected to the bus, with theresult that the switching states of at least one of the sensors andidentification data of the sensors can be called up and transmitted viathe bus.
 4. A safety apparatus according to claim 1, wherein at leastone of the sensors has a contact bridge and a contact receptacle forreceiving the contact bridge, said contact bridge being arranged suchthat the closing state of the elevator door can be determined byconnection of the contact receptacle and the contact bridge, the sensorbeing in the form of an optical sensor which comprises a transmitter fortransmitting an optical signal and a receiver for receiving the opticalsignal, the transmitter and the receiver being arranged on the contactreceptacle and the contact bridge comprising at least one transmissionelement for transmitting the optical signal.
 5. A safety apparatusaccording to claim 1, wherein the first safety circuit comprises atleast one electromechanical switch.
 6. A safety apparatus according toclaim 1, wherein at least two of the sensors are connected in series. 7.A safety apparatus according to claim 1, further comprising an indicatorapparatus for displaying the switching state of the individual sensorswith assignment of the individual switching states to the correspondingsensors.
 8. A safety apparatus according to claim 1, further comprisingan indicator apparatus that is connected to the bus and indicates, onthe basis of the switching states and identification data, at least oneof which sensors have which switching state and which sensor has aspecific switching state.
 9. A safety apparatus according to claim 1,wherein the switching unit performs communication with the sensors by atleast one of modulation of the current intensity and the voltage.
 10. Asafety apparatus according to claim 1, wherein the sensor performsmodulation of its internal resistance for communication with theswitching unit.
 11. An elevator apparatus with a cab and at least oneelevator door for opening and closing the cab and with a safetyapparatus for locking the elevator door during operation, wherein thesafety apparatus and a sensor are provided according to claim
 1. 12. Theelevator apparatus according to claim 11, wherein the contact bridge isfitted to at least one of the elevator doors and the contact receptacleis fitted to the cab.
 13. A method for retrofitting a safety apparatusaccording to claim 1 in an elevator apparatus.
 14. The method accordingto claim 12, wherein the elevator apparatus further comprises a safetycircuit with at least one normally closed switch for effecting an openor closed conduction state, wherein, in a first method step, the safetycircuit is interrupted upstream and downstream of the normally closedswitch.
 15. The method according to claim 13, wherein, in a secondmethod step, a safety device is introduced by virtue of the switchingunit being used instead of the normally closed switch and the switchingunit being connected to the safety device.
 16. A retrofitting apparatusfor retrofitting safety apparatuses of elevator apparatuses with safetycircuits, said retrofitting apparatus comprising: a series circuitcomprising normally closed switches, a safety device that comprises atleast two sensors, wherein the sensors are switched between at least twoswitching states depending on the closing state of an elevator door, anda switching unit that can be switched between at least two switchingstates by connection to the safety device, wherein the switching unit isinserted into the safety circuit instead of at least one of the normallyclosed switches, wherein the switching state of each sensor isdeterminable by the switching unit independent of the switching statesof the at least two sensors.